Cotton thrives in warm, frost-free climates with long growing seasons, typically needing five to six months of sustained heat to progress from seedling to harvestable boll. The crop is best suited to subtropical and warm-temperate regions where daytime temperatures regularly sit between about 25 °C and 35 °C (roughly 77–95 °F) during the growing season, rainfall or irrigation delivers adequate moisture at the right times, and abundant sunshine fuels fiber development. But “warm climate” only sketches the outline. The specifics of soil temperature at planting, the exact heat thresholds that damage flowers, and how much water is actually enough reveal a more demanding set of requirements than the broad label suggests.
Temperature Is the Master Variable
More than any other single factor, temperature dictates where cotton can and cannot be grown commercially. The crop originates from tropical and subtropical ancestors, and its physiology still reflects that heritage. Cotton breeders and agronomists track accumulated heat over the season using degree-day calculations, essentially a running tally of how much warmth the crop receives each day above a base temperature. In the United States, the traditional system counts heat units above a base of 60 °F (roughly 15.5 °C), although recent field research suggests that a base of 55 °F with an upper ceiling of 86 °F may predict actual growth-stage timing slightly better.1Agronomy Journal. Reevaluation of the degree day base 60°F concept in US cotton (Gossypium hirsutum L.) production The practical takeaway is the same either way: cotton needs a lot of accumulated warmth, and regions with short, cool summers simply cannot deliver it.
In northwest India, one of the world’s major cotton-producing zones, baseline accumulated heat during the growing season ranges from about 2,070 to 2,440 °C-days depending on the sub-region.2Journal of Water and Climate Change. Climate change impact assessment of growing degree days and thermal growing period of cotton in north-west India That gives a rough sense of the thermal budget cotton demands. Regions that consistently fall short of those totals, whether due to latitude, altitude, or persistent cloud cover, are not viable cotton country without season-extending technology like plastic mulch or short-season cultivars.
Soil Temperature and the Planting Window
Even in a warm climate, the timing of spring planting is governed by soil temperature rather than air temperature. Cotton seed placed in cold soil germinates slowly if it germinates at all, and disease risk climbs sharply. The generally accepted minimum soil temperature for planting is 60 °F (about 15.5 °C), but many agronomists push that higher: planting is often not recommended until soil reaches 68 °F (20 °C) because cooler soils dramatically increase the chance of seedling disease.3Agricultural and Forest Meteorology. The critical role of temperature in determining optimal planting schedule for cotton: A review In Texas, the guideline is a ten-day average of 64 °F at the eight-inch depth, bumped up to 70 °F if seed quality is questionable.3Agricultural and Forest Meteorology. The critical role of temperature in determining optimal planting schedule for cotton: A review
Lab and field trials back this up quantitatively. Raising the minimum soil temperature from 50 °F to 64 °F has been shown to lift seedling emergence and survival from roughly 56% to 90%, while cutting the time to full emergence from 29 days down to just 5.3Agricultural and Forest Meteorology. The critical role of temperature in determining optimal planting schedule for cotton: A review Seeds germinate best between 25 °C and 35 °C, with germination notably hindered below 15 °C and above 40 °C.4International Journal of Energy and Environmental Science. The Impact of Temperature on Cotton Seed Germination Brazilian research narrows the optimum even further to 28–30 °C, noting that germination percentages drop significantly only once temperatures fall below 20 °C.5Revista Brasileira de Sementes. Germination of cotton seed in relation to temperature
For anyone choosing when and where to plant, the message is clear: cotton needs warm ground, not just warm air. A region can have perfectly adequate summer temperatures but still be marginal for cotton if late-spring soil stays cool too long, shaving weeks off the effective growing season.
When Heat Becomes the Enemy
Cotton loves heat, but there is a ceiling. Once temperatures push above roughly 35 °C (95 °F) during flowering, the crop’s reproductive biology starts to break down. Pollen is the weak link. Research on upland cotton in China found that pollen germination rates dropped significantly when maximum daily temperatures hit 35 °C or higher for three consecutive days.6Agronomy Journal. High Temperature Reduces the Viability of Pollen from Upland Cotton in China A multi-cultivar study measuring heat stress effects reported pollen germination falling by about 71% across cultivars compared to control conditions. Even cultivars that maintained similar boll and seed numbers under heat stress did not maintain their seed cotton yield, meaning the damage showed up as lighter, lower-quality bolls rather than fewer of them.7PubMed Central. Intensifying heat stress impacts cotton flowering and boll development efficiency
This creates a surprisingly narrow thermal sweet spot for cotton at its most vulnerable growth stage. Flowering benefits from warm days in the low 30s °C but suffers once temperatures consistently spike above 35 °C. In practice, that means the world’s hottest cotton regions, parts of Pakistan, Sudan, and the American Southwest, sometimes face yield penalties not from a lack of heat but from too much of it, particularly during heat waves that coincide with peak bloom.
How Much Water Cotton Actually Needs
Cotton is sometimes called drought-tolerant, and compared to many field crops it does handle dry spells reasonably well. Its deep taproot can pull moisture from well below the surface. But calling it drought-proof would be a stretch. Water-deficit stress during flowering and boll development has a clear negative relationship with final yield.8Journal of Cotton Science. Assessment of Cotton Leaf and Yield Responses to Water-Deficit Stress During Flowering and Boll Development The crop can tolerate dry conditions early and late in the season far better than it can during the critical weeks when bolls are filling.
Globally, cotton is grown under both irrigated and rainfed conditions. Comparing the two, fiber quality traits like length, strength, and uniformity remain remarkably consistent regardless of whether water comes from rain or a pivot, with correlations above 0.95 between irrigated and rainfed environments in multi-site trials. Lint yield, however, tells a different story: the correlation between irrigated and rainfed environments is only moderate, reflecting the fact that total fiber output is much more sensitive to water supply than fiber quality is.9Field Crops Research. Genotype × environment interaction and multi-trait stability of cotton lint yield and fiber quality across irrigated and rainfed environments
Soil texture matters here, too. Sandy soils drain quickly and hold less plant-available water, amplifying drought risk. Field trials comparing precision irrigation to conventional and rainfed management found a strong effect of sand content on cotton yield, sometimes outweighing the irrigation treatment itself.10Precision Agriculture. Comparison of precision and conventional irrigation management of cotton and impact of soil texture So the “right” rainfall for cotton depends heavily on local soil type. A region receiving 600 mm of growing-season rain might produce excellent rainfed cotton on a clay loam but disappointing yields on a sandy field next door.
As a rough guide, cotton typically requires somewhere between 500 and 1,200 mm of water over the full growing season, with the wide range reflecting differences in evaporative demand, soil water-holding capacity, and growing-season length. The key pattern is that cotton can tolerate dryness but rewards adequate moisture during boll fill, making semi-arid climates with supplemental irrigation some of the highest-yielding cotton environments in the world.
Sunlight and Light Availability
Cotton is a sun-loving crop. Carbohydrate production and reproductive structure development depend directly on light availability, which determines how much energy the plant has to invest in fiber growth.11European Journal of Agronomy. Cotton yield and fiber quality affected by row spacing and shading at different growth stages Persistent cloud cover during the boll-filling period reduces both yield and fiber quality, which is one reason the crop performs best in climates with high solar radiation during summer months. Self-shading from overly dense plant populations mimics the effect of clouds, something growers manage through row spacing.
Most major cotton regions sit at latitudes that deliver strong summer sunshine: the U.S. Cotton Belt, Central Asia’s Fergana Valley, the Indus and Nile valleys, and interior Brazil all share a combination of long days and high solar intensity during the growing season. Regions with monsoonal climates can grow cotton, but persistently overcast skies during critical reproductive windows sometimes limit yield potential.
Where Cotton Grows Around the World
The global cotton map falls broadly between about 37°N and 32°S latitude, stretching from the southern United States through West Africa, the Mediterranean fringe, the Indian subcontinent, Central Asia, China, and parts of Australia and South America. Within that band, production concentrates in regions combining the thermal budget, sunshine, and seasonal water patterns cotton requires.
In the United States, the “Cotton Belt” runs from the Carolinas through the Deep South and west into Texas, Oklahoma, New Mexico, Arizona, and California’s San Joaquin Valley. Modeling work has shown that a physics-based crop model can reproduce long-term mean cotton yields within about 10% of observed values across virtually the entire U.S. Belt, confirming that regional climate characteristics are the dominant driver of yield geography. The same modeling found that July-to-August air temperature and August-to-September soil temperature anomalies are particularly strong predictors of year-to-year yield swings on unirrigated land.12Agronomy Journal. Physical Modeling of U.S. Cotton Yields and Climate Stresses during 1979 to 2005 That finding underscores how tightly cotton yield is coupled to climate, not just in the average but in every individual season.
Australia grows cotton primarily in inland New South Wales and Queensland, relying on a combination of irrigation and naturally warm, dry growing conditions. China’s cotton production spans from the Yangtze River Delta (humid subtropical) to the arid irrigated basins of Xinjiang. India’s cotton zone spans Gujarat, Maharashtra, Andhra Pradesh, and Punjab, mixing rainfed and irrigated systems across a range of semi-arid to monsoon-influenced climates. Each region adapts variety selection, planting dates, and water management to its local version of “cotton climate.”
How Climate Change Is Reshaping Cotton Geography
Rising temperatures are already altering the conditions cotton encounters. In northwest India, projected warming by mid-century is expected to increase accumulated growing degree-days by anywhere from 3% to 27% depending on the sub-region and emissions scenario, potentially shortening the thermal growing period by 6–25%.2Journal of Water and Climate Change. Climate change impact assessment of growing degree days and thermal growing period of cotton in north-west India A shorter thermal growing period sounds harmless, but it means the crop races through its developmental stages faster, with less time to accumulate biomass and fill bolls. The result is thermal stress, not thermal advantage.
In Australia, trend analysis across major cotton regions has found reductions in early-season cold shocks (minimum temperatures at or below 11 °C), increases in minimum temperature and seasonal heat accumulation, and a rise in the frequency of extremely high temperatures above 40 °C. Time to first flower has decreased at several locations, which could either help (by allowing longer reproductive periods) or hurt (by reducing pre-flowering leaf area), depending on the site.13Field Crops Research. The here and now of climate change: Climatic trends throughout Australian cotton regions and implications for the growing season
The big-picture expectation is that cotton’s viable range may shift poleward as higher latitudes warm enough to support the crop, while some currently productive tropical and subtropical zones may tip past the heat-stress thresholds described earlier. Whether growers can adapt through breeding heat-tolerant cultivars, adjusting planting dates, or expanding irrigation remains an open and region-specific question.
Pests That Track Temperature
Climate does not just determine how well cotton grows; it also governs the pest pressure the crop faces. The cotton bollworm, one of the most damaging insects worldwide, is sensitive to temperature extremes in ways that shape regional population dynamics. Research across three cotton-growing regions in China’s Xinjiang province found that winter temperature was the single most influential climate variable on bollworm population sizes in at least one region, explaining up to 98% of interannual variation. Summer temperatures below 33 °C tended to boost bollworm populations, while temperatures above 33 °C suppressed them.14MDPI Insects / PubMed Central. Temperature Changes Affect the Vulnerability of Cotton Bollworms, Helicoverpa armigera (Hübner)
The interaction between winter and summer temperatures creates complicated and sometimes counterintuitive outcomes. Warmer winters might reduce spring bollworm emergence in some areas but increase annual populations in others. For cotton growers, the upshot is that climate shifts do not just change how the crop itself performs; they reshuffle the pest deck, potentially increasing insect pressure in regions that previously had natural cold-season suppression.
Salt Tolerance and Marginal Growing Environments
One reason cotton has spread into so many semi-arid and arid irrigated regions is its relatively high tolerance for soil salinity. Cotton is classified as moderately salt-tolerant, with a salinity threshold around 7.7 dS/m, well above what most grain crops can handle. That said, sensitivity depends on growth stage: germination, emergence, and seedling stages are considerably more vulnerable to salt stress than later stages.15PubMed Central. Salinity stress in cotton: effects, mechanism of tolerance and its management strategies Salinity remains a serious threat to yield and fiber quality even in a crop considered tolerant, particularly in irrigated systems where salts accumulate over years of water application.
In arid climates, the combination of high evaporation and repeated irrigation cycles concentrates salts in the root zone. This is a growing problem in regions like Central Asia’s Aral Sea basin, parts of Pakistan’s Punjab, and Australia’s inland irrigation districts. Cotton’s salt tolerance gives it a role as one of the few viable commercial crops on moderately saline land, but that tolerance has limits, and climate-driven increases in evaporative demand could push more fields beyond them.
Waterlogging and Flooding Tolerance
While drought gets most of the attention, the opposite extreme matters too. Cotton does not handle waterlogged soils well, and flooding during the growing season can devastate yields. However, there is meaningful genetic variation in how different cotton types respond. Field trials comparing Pima cotton (Gossypium barbadense) and upland cotton (Gossypium hirsutum) found that Pima cotton showed no leaf color changes even seven days after waterlogging, indicating high short-term tolerance. Upland cotton, the species that accounts for the vast majority of global production, showed a wide range of tolerance among cultivars.16Industrial Crops and Products. Genetic variation of waterlogging tolerance in Pima (Gossypium barbadense) cotton and glanded and glandless Upland cotton (Gossypium hirsutum) under field conditions
This matters for climate suitability because many cotton regions experience intense monsoon rains or periodic flooding. In India’s Maharashtra or parts of the U.S. Mississippi Delta, fields can sit in standing water for days after heavy rain. Choosing cultivars with better waterlogging tolerance is one way growers in flood-prone climates manage the risk, but the fundamental reality remains: cotton prefers well-drained soils and performs best when its roots have access to oxygen.
Wild Cotton and Its Ecological Roots
Understanding cotton’s climate preferences becomes more intuitive when you look at where it evolved. The wild ancestor of upland cotton, Gossypium hirsutum, is native to tropical and subtropical environments in Mesoamerica and the Caribbean basin. Populations of genuinely wild upland cotton still exist, including one on Mound Key in southwestern Florida. Genetic analysis of this population found that it exhibited the highest genetic divergence from domesticated cotton groups, even more than other recognized wild populations, consistent with it being a truly wild remnant rather than a feral escapee from cultivation.17PubMed Central. Origin and diversity of the wild cottons (Gossypium hirsutum) of Mound Key, Florida
That a wild cotton population persists on a subtropical Florida shell island is telling. The warm, humid, frost-rare environment of the Gulf Coast is essentially what this plant evolved for. Every climate requirement of commercial cotton, the long frost-free season, warm soil at planting, intense summer heat and sunlight, tolerance for periodic drought punctuated by heavy rain, maps back to the conditions of its ancestral habitat. Domestication and breeding have stretched those boundaries somewhat, allowing cotton to succeed in drier and slightly cooler climates with the help of irrigation and short-season varieties. But the fundamental biology remains rooted in the tropics, and that ancestry explains why the crop resists every attempt to push it into climates that stray too far from warm, sunny, and frost-free.